1. Field of the Invention
The present invention generally relates to a vehicle seat structure. In particular, the invention is directed to a structure of vehicle seat which is effective in withstanding a great load and also applicable to a fold-down vehicle seat which allows its seat back and seat cushion to be folded or flipped over into a full-flat seat state.
2. Description of Prior Art
Among various sorts of vehicle seats, there is known a folding or fold-down seat structure wherein a seat back frame and/or a seat cushion frame are/is foldable into a compact folded state to widen a space in a vehicle. Also, known is a full-flat type of fold-down seat structure wherein a seat back frame and a seat cushion frame are both so articulated on a base frame as to be foldable into a full-flat state where the rear surfaces of the seat back and cushion frames lie generally flush with each other to provide an enlarged floor or cargo load space in the rearward cabin region of a vehicle.
Typically, those seat structures are provided with a pair of slide rails, each comprising a lower rail fastened on a vehicle floor and an upper rail slidably fitted in the lower rail, such that the upper rail is in a locking relation with the lower rail via a lock mechanism, with a striker provided in that upper rail (as disclosed from the Japanese Laid-Open Patent Publication No. 11-278117 for example). In the full-flat type fold-down seat structure, the lower rail is disposed subjacent to the base frame, whereas the upper rail is fixedly attached to the same base frame, with a striker being provided in the upper rail. In any case, the seat cushion frame is normally provided with a seat belt and pivoted on a forward end of base frame at the forward end thereof, thereby being free to rotate or flip over in the forward direction relative to the base frame. Further, the seat cushion frame is provided with a latch at the rearward end thereof, which is adapted for releasable engagement with the striker provided in the upper rail. In the case of full-flat-type fold-down seat, its seat back frame is so pivoted on the rearward end of the base frame as to be foldable down onto the base frame.
According to such conventional seat frame structures, in a resultant upholstered vehicle seat produced therefrom, a user or passenger can release the latch provided in its seat cushion from engagement with the striker to flip over the seat cushion forwardly together with the seat belt into a reversed state where the planar rear side of seat cushion is exposed and lies generally flat. In particular, in the full-flat-type fold-down seat, the user or passenger can also fold the seat back forwardly into a reversed state upon the base frame, in which the planar rear side of the seat back is exposed and set substantially in registry with the seat cushion back side, with the result that the seat on the whole is made full flat to define a cargo load floor or load-carrying platform in the vehicle cabin.
However, the foregoing conventional seat structures, due to the seat cushion being latched to the striker provided in the slide rail, has been found defective in requiring that the slide rails themselves be greatly reinforced with its extremely increased thickness to withstand a great load input from the seat belt to the seat cushion frame when a collision or sudden deceleration occurs, which leads to an undesirable increase of the weight of seat.
To solve such problem, it has been contemplated that the anchor of seat belt is secured directly to the floor of vehicle. But, in that case, it is necessary and quite troublesome for a user or passenger to relocate the seat belt to the seat cushion every time he or she moves the seat in the fore-and-aft direction and/or flips over the seat cushion between a normal use position and a reversed flat state. This is because the seat belt will naturally fall under the seat cushion during that seat positioning/folding operation, thus making it annoyingly necessary for the user or passenger to reach out for the fallen seat belt, pick it up and put it on the seat cushion again.
With the above-stated drawbacks in view, it is therefore a primary purpose of the present invention to provide an improved structure of vehicle seat which realizes its light weight with sufficient robustness and also prevents a seat belt being fallen and missing from its seat cushion when moving and/or folding the seat.
To achieve such purpose, a structure of vehicle seat in accordance with the present invention basically comprises:
a pair of slide rail devices including a lower rail fixed on a floor of vehicle and an upper rail slidably engaged with the lower rail;
a base frame integrally fixed to the upper rail, which base frame has a forward end facing to a side forwardly of the seat;
a seat cushion frame pivotally connected with the forward end of base frame such as to be rotatable forwardly and backwardly relative to that forward end, which seat cushion frame has a rearward area facing to a side rearwardly of the seat;
a striker means fixedly provided on the floor;
a lock mechanism for locking and unlocking the seat cushion frame to and from the striker; and
a seat belt means;
wherein the lock mechanism is provided in the rearward area of seat cushion frame and wherein the seat belt means is securely attached to the seat cushion frame in an integral manner together with the lock mechanism.
Accordingly, in the case of collision or sudden deceleration, a great load, applied to the seat from an occupant thereon who is restrained by the seat belt means, is imparted via the seat belt means to the seat cushion frame and quickly escaped through the lock means and striker down to the vehicle floor. Since the great load is directly exerted upon the floor or vehicle body, the seat cushion frame does not require any special reinforcement that involves a whole increased physical modification thereof, thus allowing the seat cushion frame to remain unchanged or light in weight. Also, the provision of seat belt means at the seat cushion frame insures to not only make the seat belt means readily accessible to a user or passenger even when he or she is adjusting the seat fore-and-aft position and folding the seat, but also preclude the seat belt means from being fallen down through the seat during that seat arranging work, which therefore avoids the troublesome necessity for user or passenger to find and reach out for the seat belt means fallen or missing under the seat.
It is a second purpose of the present invention to provide a seat construction which avoids an intensive exertion of the foregoing great load upon the lock mechanism and eliminates the need for reinforcing the lock mechanism itself.
For that purpose, in the seat cushion frame, there are formed a cross frame member and a longitudinal frame member extending in a direction transversely of the cross frame member, and further, firmly connected with those cross and longitudinal frame members is a vertically extending base plate to which both lock means and seat belt means are fixedly attached. Thus, the great load will be dispersed effectively into those cross and longitudinal frame members as well as the base plate, thereby avoiding an intensive load exertion on the lock mechanism and seat belt means, while simultaneously allowing direct and smooth escape of the load to the floor.
Other features and advantages of the present invention will become apparent from reading of the description hereinafter, with reference to the annexed drawings.